Urinary incontinence affects millions of people, causing discomfort and embarrassment, sometimes to the point of social isolation. In the United States, recent studies have shown that as many as 25 million persons, of whom approximately 85% are women, are affected by bladder control problems. Incontinence occurs in children and young adults, but the largest number affected are the elderly.
There are several major forms of incontinence:                Stress incontinence is an involuntary loss of urine while doing physical activities which put pressure on the abdomen. These activities include exercise, coughing, sneezing, laughing, lifting, or any body movement which puts pressure on the bladder. Stress incontinence is typically associated with either or both of the following anatomical conditions:        
Urethral hypermobility—Weakness of or injury to pelvic floor muscles causes the bladder to descend during abdominal straining or pressure, allowing urine to leak out of the bladder. This is the more common source of stress incontinence.
Intrinsic sphincter deficiency—In this condition, the urethral musculature is unable to completely close the urethra or keep it closed during stress.                Urge incontinence is the sudden urgent need to pass urine, and is caused by a sudden bladder contraction that cannot be consciously inhibited. This type of incontinence is not uncommon among healthy people, and may be linked to disorders such as infections that produce muscle spasms in the bladder or urethra. Urge incontinence may also result from illnesses that affect the central nervous system.        Overflow incontinence refers to leakage of urine that occurs when the quantity of urine exceeds the bladder's holding capacity, typically as a result of a blockage in the lower urinary tract.        Reflex incontinence is the loss of urine when the person is unaware of the need to urinate. This condition may result from nerve dysfunction, or from a leak in the bladder, urethra, or ureter.        
Of the major forms of incontinence listed above, the two most common are stress and urge. “Mixed incontinence” is a term used to describe the common phenomenon of the presence of stress and urge incontinence in the same patient.
A large variety of products and treatment methods are available for care of incontinence. Most patients suffering from mild to moderate incontinence use diapers or disposable absorbent pads. These products are not sufficiently absorbent to be effective in severe cases, are uncomfortable to wear, and can cause skin irritation as well as unpleasant odors. Other non-surgical products for controlling incontinence include urethral inserts (or plugs), externally worn adhesive patches, and drugs.
Exercise and behavioral training are also effective in some cases in rehabilitating pelvic muscles and thus reducing or resolving incontinence. Patients are taught to perform Kegel exercises to strengthen their pelvic muscles, which may be combined with electrical stimulation of the pelvic floor. Electromyographic biofeedback may also be provided to give the patients an indication as to the effectiveness of their muscular exertions. But retraining muscles is not possible or fully effective for most patients, particularly when there may be neurological damage or when other pathologies may be involved.
Medtronic Neurological, of Columbia Heights, Minn., produces a device known as Interstim, for treatment of urge incontinence. Interstim uses an implantable pulse generator, which is surgically implanted in the lower abdomen and wired to nerves near the sacrum (the bone at the base of the spine) in a major surgical procedure—sometimes six hours under general anesthesia. Electrical impulses are then transmitted continuously to a sacral nerve that controls urinary voiding. The continuous electrical stimulation of the nerve has been found to control urge incontinence in some patients.
Various surgical procedures have been developed for bladder neck suspension, primarily to control urethral hypermobility by elevating the bladder neck and urethra. These procedures typically use bone anchors and sutures or slings to support the bladder neck. The success rates for bladder neck suspension surgery in controlling urinary leakage are typically approximately 60%-80%, depending on the patient's condition, the surgeon's skill, and the procedure which is used. The disadvantages of this surgical technique are its high cost, the need for hospitalization and long recovery period, and the frequency of complications.
For serious cases of intrinsic sphincter deficiency, artificial urinary sphincters have been developed. For example, the AMS 800 urinary sphincter, produced by American Medical Systems Inc., of Minnetonka, Minn., includes a periurethral inflatable cuff, which is used to overcome urinary incontinence when the function of the natural sphincter is impaired. The cuff is coupled to a manually-operated pump and a pressure regulator chamber, which are implanted in a patient's body together with the cuff. The cuff is maintained at a constant pressure of 60-80 cm of water, which is generally higher than the bladder pressure. To urinate, the patient releases the pressure in the cuff. Aspects of this system are described in U.S. Pat. No. 4,222,377 to Burton, which is incorporated herein by reference.
This artificial sphincter has several shortcomings, however. The constant concentric pressure that the periurethral cuff exerts on the urethra can result in impaired blood supply to tissue in the area, leading to tissue atrophy, urethral erosion and infection. Furthermore, the constant pressure in the cuff is not always sufficient to overcome transient increases in bladder pressure that may result from straining, coughing, laughing or contraction of the detrusor muscle. In such cases, urine leakage may result.
U.S. Pat. Nos. 4,571,749 and 4,731,083 to Fischell, which are incorporated herein by reference, describe an artificial sphincter device whose pressure can vary in response to changes in abdominal or intravesical (bladder) pressure. The device includes a periurethral cuff, subdermic pump, pressure regulator, and hydraulic pressure sensor.
U.S. Pat. No. 3,628,538 to Vincent et al., which is incorporated herein by reference, describes apparatus for stimulating a muscle based on an electromyographic (EMG) signal sensed in the muscle. If the signal is greater than a predetermined threshold value, a stimulator circuit applies a voltage to electrodes adjacent to the muscle. The apparatus is said to be particularly useful in overcoming incontinence.
U.S. Pat. No. 6,135,945 to Sultan, which is incorporated herein by reference, describes apparatus for preventing uncontrolled discharge of urine from a patient's urethra. The apparatus includes an implantable pressure sensor for sensing intra-abdominal pressure, which generates a pressure signal in response to the sensed pressure. An actuating device is coupled to the pressure sensor, and generates an electrical signal in response to the pressure signal. A controller is coupled to the actuating device, and is configured to selectively compress the patient's urethra and thereby prevent incontinence.
Various types of electrodes have been proposed for applying electrical stimulation to pelvic muscles so as to prevent unwanted urine flow. For example, U.S. Pat. No. 5,562,717 to Tippey et al. describes electrodes that are placed on the body surface, typically in the areas of the perineum and the sacrum, and are electrically actuated to control incontinence. U.S. Pat. No. 4,785,828 to Maurer describes a vaginal plug having electrodes on an outer surface thereof. A pulse generator in the plug applies electrical pulses to the electrodes so as to constrict the patient's pelvic muscles and prevent urine flow. U.S. Pat. No. 4,153,059 to Fravel et al. describes an intra-anal electrode, to which repetitive electrical pulses are applied in order to control urinary incontinence. U.S. Pat. No. 4,106,511 to Erlandsson describes an electrical stimulator in the form of a plug for insertion into the vagina or the anus. U.S. Pat. No. 3,866,613 to Kenny et al. describes a pessary ring having two electrodes thereon, which are energized to control incontinence. U.S. Pat. No. 4,406,288 to Horwinski et al. describes apparatus for conditioning the pelvic floor musculature to reduce bladder contractility and relax the bladder, so as to prevent involuntary urinary loss. All of the above-mentioned patents are incorporated herein by reference.
U.S. Pat. No. 4,580,578 to Barson, which is incorporated herein by reference, describes a device for stimulating the sphincter muscles controlling the bladder. A supporting body is fitted into the patient's vulva between the labia, so that two electrodes attached to the supporting body contact the epidermal surface on either side of the external urethral orifice. Electrical impulses are applied to the electrodes to stimulate the region of the sphincter.
U.S. Pat. No. 4,607,639 to Tanagho et al., which is incorporated herein by reference, describes a method for controlling bladder function by nerve stimulation, typically of a sacral nerve. The anatomical location of at least one nerve controlling the muscles for the bladder and/or its sphincter is identified, and an electrode is placed on the nerve to selectively stimulate the nerve for continence and evacuation purposes.
U.S. Pat. No. 4,739,764 to Lue et al., which is incorporated herein by reference, describes a system for electrical stimulation of nerves in order to treat urinary incontinence, fecal incontinence, interstitial cystitis, and other pelvic pain syndromes.
U.S. Pat. No. 6,240,315 to Mo et al., which is incorporated herein by reference, describes incontinence treatment apparatus which includes a module for evaluating a recorded EMG signal.
U.S. Pat. No. 5,484,445 to Knuth, which is incorporated herein by reference, describes a system for anchoring a lead to the sacrum for purposes of long-term stimulation, typically for treatment of incontinence.
U.S. Pat. Nos. 5,927,282 and 6,131,575 to Lenker et al., which are incorporated herein by reference, describe removable external closures for the urethra as means for relieving or mitigating incontinence problems.
U.S. Pat. No. 6,002,964 to Feler et al., which is incorporated herein by reference, describe a method for managing chronic pelvic pain. The method includes techniques for positioning one or more stimulation leads within or about the sacrum to enable electrical energy to be applied to spinal nervous tissue, including nerve roots, in order to inhibit the transmission of pain signals.
An article by Fall et al., entitled, “Electrical stimulation in interstitial cystitis,” Journal of Urology, 123(2), pp. 192-195, Feb. 1980, which is incorporated herein by reference, describes a study in which fourteen women with chronic interstitial cystitis were treated with long-term intravaginal or transcutaneous nerve stimulation. Clinical and urodynamic evaluations were performed after 6 months to 2 years. Improvement was not immediate, but required a considerable period of continuous, daily use of electrical stimulation.
An article by Zermann et al., entitled, “Sacral nerve stimulation for pain relief in interstitial cystitis,” Urol. Int., 65(2), pp. 120-121, 2000, which is incorporated herein by reference, describes a case in which a 60-year-old woman was treated for severe interstitial cystitis pain using sacral nerve stimulation.
An article by Chai et al., entitled, “Percutaneous sacral third nerve root neurostimulation improves symptoms and normalizes urinary HB-EGF levels and antiproliferative activity in patients with interstitial cystitis,” Urology, 55(5), pp. 643-646, May, 2000, which is incorporated herein by reference, notes: “A highly effective treatment for interstitial cystitis (IC) remains elusive. . . . Results suggest that permanent S3 PNS may be beneficial in treating IC.”
An article by Caraballo et al., entitled, “Sacral nerve stimulation as a treatment for urge incontinence and associated pelvic floor disorders at a pelvic floor center: a follow-up study,” Urology, 57(6 Suppl 1), p. 121, June, 2001, which is incorporated herein by reference, describes and presents the results of an additional study in which sacral nerve stimulation was applied in an effort to treat urinary incontinence.
PCT Patent Publication WO 00/19939, entitled, “Control of urge incontinence,” which is assigned to the assignee of the present patent application and incorporated herein by reference, describes a device for treatment of urinary urge incontinence, in which imminent urge incontinence is sensed, and a pelvic nerve or muscle is stimulated to inhibit the flow.
PCT Patent Publication WO 00/19940, entitled, “Incontinence treatment device,” which is assigned to the assignee of the present patent application and incorporated herein by reference, describes a device for treating urinary stress incontinence, in which imminent involuntary urine flow is sensed, and a pelvic nerve or muscle is stimulated to inhibit the flow.
A book entitled Urinary Incontinence, edited by P. O'Donnell, Mosby Publishers, 1997, which is incorporated herein by reference, describes clinical aspects relating to the diagnosis and treatment of urinary incontinence.